Composite illumination device



July 26 1966 G. K. c. HARDEsTY COMPOSITE ILLUMINATION DEVICE OriginalFiled Dec. '7. 1960 INVENTOR.

HA RDES T Y 7 r ATTY United States Patent O 3,262,224 COMPOSITEILLUMINATION DEVICE George K. C. Hardesty, P.0. BOX 156, Mayo, Md.Original application Dec. 7, 1960, Ser. No. 74,438. Divided and thisapplication Sept. 29, 1964, Ser. No. 404,546

Z Claims. (Cl. 40-130) The present application is a divisionalapplication of applicants `co-pending application Serial No. 74,438,iiled December 7, 1960.

The invention described herein may the manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The present invention relates to panel illumination and moreparticularly to the illumination of control console indicators underconditions running from near or total darkness to high ambientillumination Many critical equipment failures or other emergencyconditions can result fr-m the complexities of modern aircraft,shipboard, land missile control equipment. To protect the ship oraircraft or missile and the personnel who must Work around it continuousmonitoring and alarm systems have been progressively developed. Severaltypes of these monitoring and alarm systems employ audible signals toattract attention of personnel but in some instances there is`ditiiculty in providing distinctively different audible signals lforeach of the monitors. In other instances, as in the submarine, audiblesignals must -be silent for long periods and reliance placed on silentwarning signals. Available visual signals, however, do not cover thenecessary range of application needs. There is little available to theship or 4aircraft designer between the pilot or indicator ligh and thelarge rotating flashing signals of the familiar police squad car oramlbulance. Conspicuous, attention demanding, legend displays, which arecompact and inexpensive, are needed to provide many shipboard and shoreinstallations with adequate monitor warning signal systems.

Many types of indicator lights and p'anel illumination devices have beensuggested for use on control consoles. The failure of many existingindicator displays to be discernible in high ambient illumination hasbeen the cause of much concern in both shipboard and aircraftsituations. When a number of conventional indicator lights are groupedtogether, the total array is too bright for comfort for near-darkadaptation viewing. Further, the full significance of the light beingenergized is often a matter of training and memory because it has notbeen possible heretofore to read the legends on nearby nameplates withprevalent ambient illumination. Some dim-out cap assemblies utilizeback-lighted, stencilled, legend discs lbut their use entails a sharpreduction of maximum brightness that depreciates the effectiveness ofthe signal, particularly in the higher ambient illumination nowprevalent in new submarine construction. Translucent signal panels havein the past been rear illuminated by lamps placed fbehind the panel.However, such attempts at rear illumination invari-ably have resulted inuneven ineffective illumination if the lamps are .placed close to therear panels, or vastly reduced brightness if the lamps are sufficientlyremoved from the panels to result in reasonably uniform brightness. Itshould also be noted that in some instances, suflicient space is notavailable behind the console panel for removal of these lamps in case oflamp failure The present invention permits efficient presentation ofdisplays which are particularly suitable for use in high ambientillumination conditions. The underlying optical system is capable of usewith various types of illumination sources with greater eliiciency inboth power and space than was possible with most prior art devices.

3,262,224 Patented July 26, i966 The illumination provided by thisinvention achieves uniform high brightness displays that are suitablefor use in control and monitoring applications where the uneven,ineffective displays which were prevalent in many prior art devices arevirtually useless. These advantages are provided basically by aclosed-loop or reentrant optical circuit wherein the light source isshielded from the indicia to be illuminated lby an opaque barrier. Inaccordance with the invention, light from the light source is carriedaround the opaque shield, in accordance with the laws of total internalreflection, by a transparent light transmitting element.

Accordingly, it is an object of the present invention to provide animproved illuminated signal device adequate for use under conditions ofhigh ambient illumination as well as under conditions of near or totaldarkness.

Another object is the provision of a system for effecting local zones ofrear illumination in translucent signal panels with the result thatuniform brightness symbols on the panels may be selectively illuminatedin accordance with the needs of a monitoring or control equipment.

A further object of the invention is to provide a smallilluminated-legend, indicating module capable of presenting informationwithout the need for auxiliary nameplate interpretation.

Still another object is the provision of a legend display which will ybeconspicuous, attention demanding, compact, inexpensive, and optionallycapable of presenting the displayed information in a series of codedcolors.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with 4the accompanying drawings wherein:

FIG. 1 is a sectional view of one embodiment of the present invention;

FIG. 2 is a sectional view of a modified device similar in concept toFIG. l; and

FIG. 3 is a sectional view of another embodiment of the invention.

Referring now to FIG. l, there is shown an embodiment of the inventionin the form of a display device 10 wherein a plurality of differenttypes of light sources are utilized. The display device 10 comprises alight source in the form of lamp Sil mounted in an aperture 32 in alight input panel 36 having a reflective beveled edge 37 cooperatingwith the reliective lbeveled edge 38 on an edge lighted display element40. On display element 40 are provided a number of engraved indicia 41.The assembly of elements 36 and 40 is held in an enclosing housing orlight shield 44 which may be mounted on any suitable control panel. In acavity 4S defined between the elements 36 and 40 there is provided anelectroluminescent element 46 which has its light emitting side facingthe light input element 36 and also has a. black coating on the surfacefacing the edge lighted display element 4t). The black coating on theelectroluminescent element 46 serves as an opaque light ybarrier whichprevents light from passing from the lamp 30 directly through displayelement 40.

A second electroluminescent light source 48 is placed adjacent theopposite face of light input element 36 with its light emitting sidealso facing element 36. Provided on both faces of light input element 36are a plurality of engraved light diffusing facets 50 which are designedto -direct the light emitted from the electroluminescent sources throughthe reentrant light circuit of the lamp, i.e., light input element 36and edge lighted display element 40, whereby substantially .all of thelight emitted from both electroluminescent sources and lamp source 30,except -for that portion of the light flux which is caused to be emittedfrom the lamp by indicia 41, will be continuously reflected between thereflective faces of both elements. If desired, the inside of the housingand light shield 44 may be coated with a light reective paint. lIt willalso be realized that light diffusing facets 50 may be metalized ifdesired to enhance the refiective capability.

Referring now to FIG. 2 there is shown an embodiment of the invention inthe form of a circular, plug-in, indicator module 60. The module of FG.2 comprises a pair of light sources 62, 64. The light sources 62, 64 areencapsulated directly or by means of a transparent gel or highly viscousfiuid in a clear light transmitting element 66 which is mounted forcooperation with a light carrying element 68, having reflective bevelededges 69, 70 for transmitting light from sources 62, 64 to an edgelighted disp-lay element 70 having engraved indicia.

71 to be illuminated. The elements 66, 68 may be considered together asa light input element of a light recirculating circuit including thedisplay element 70.

The light Sources 62, 64 are connected by suitable `conductors forenergization by connecting .a voltage source across prongs 73, 74 whichproject through a Wall 75 of a support member 76. The elements 66, 68,and 70 are housed as an assembly by the support member 76 and a combinedbezel, body and window member 77 which is threadedly secured at 77a tothe support member and includes a window portion 77b overlying thedisplay element 70. In addition to lamps 62, 64, there is provided anelectroluminescent panel 80 which is designed to provide a directlylighted field behind element 70 against which the indicia will besilhouetted for low ambient Viewing. It further serves as a lightbarrier to eliminate any direct lighting of indicia element 79, by lampsources 62 and 64. Additionally, the electroluminescent lamp forms `avisual background for the high luminence level edge lighted symbols orindicia '/"1 of the display element '70 when lamps 62 and 64 areenergized instead of the electroluminescent lamp. Thus, theelectroluminescent lamp may be utilized to display the tota-l area ofthe viewing window or alternatively may be used to display merely amasked off portion forming an alternate symbol to be viewed underconditions of low ambient illumination. The electroluminescent lamp 80is connected by suitable conductors, as illustrated, to prongs 81, 82 towhich suitable electrical power may be applied to energize the lamp 80to a luminescent state.

FIG. 3 shows an embodiment 90 similar in many respects to that shown inFIG. 1 but wherein a cylindrical or hemispherical element 91 isinterchanged with the disc or rectangular shaped light input element 36of FIG. 1. As s'hown in FIG. 3 light input element 91 is cylindrical orhemispherical and is designed to cooperate with the edge lighted displayelement 92 which is held in place by a 4bezel 93 on a console panel 94.The display element 92 is provided with engraved indicia 92a to beilluminated, and beveled, internally reflective edges 92h. Mountedwithin cylindrical or hemispherical light input element 91 is an opaquelight barrier 96 upon which is mounted light source 97. Anelectroluminescent panel 100 having its light emitting side facing thefront of the .assembly is mounted around the periphery of light inputelement 91 or may be an integral part of input element 91. If separateit may be more effectively coupled optically to element 91 by atransparent gel or viscous fluid. It will again be realized in thisembodiment that in place of a lamp source 97 there may be `a fluorescenttube or if element 91 is a cylindrical rather than hemispherical shape,linear sources of light such as the linear tungsten Lumiline lamp r theAperture iiourescent lamp recently developed by Sylvania ElectricProducts may be used as a light source. As required to divert light raysfor total internal refiection within 4 element 91, prismatic surfaceinterruptions similar to 50 of FIG. 1 would be provided in one or bothsurfaces of element 91.

Obviously many other modifications and variations of the presentinvention are possible in the light of the above teachings. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

I claim:

1. An indicator illumination system comprising an incandescent lamp as afirst light source and at least one electroluminescent element as asecond light source, indicia to be illuminated, said electroluminescentelement comprising an opaque light shield on one surface thereof andinterposed between said light sources and said indicia to prohibitdirect ilighting of said indicia by said light sources, a reentrantlight conducting circuit extending from said light sources to saidindicia whereby light entering said circuit from said light source isconducted through said circuit to illuminate said indicia and isrecirculated through said circuit to enhance the illumination, sai-dreentrant light conducting circuit comprising a first light conductingelement into which light from said light sources is injected, and asecond light conducting element for carrying illumination to saidindicia and cooperating with said first light conducting element toreceive light therefrom, and one of said light conducting elementshaving light refiective facets adapted to carry light around said opaquelight shield.

2. An indicator illumination system comprising an incandescent lamp as afirst light source and at least one electroluminescent element as asecond light source, indicia to be illuminated, an opaque light shieldinterposed between said light sources and said indicia to prohibitdirect lighting of said indicia by said light sources, a reentrantflight conducting circuit extending from said light sources to saidindicia whereby light entering said circuit from said light sources isconducted through said circuit to illuminate said indicia and isrecirculated through said circuit to enhance the illumination, saidreentrant light conducting circuit comprising a first light conductingelement into which light from said light sources is injected, and asecond lig-ht conducting element for carrying illumination to saidindicia and cooperating with said first light conducting element, saidsecond light conducting element having light reflective facets adaptedto carry light around said opaque light shield, said first lightconducting element being semi-circular in section, and saidelectroluminescent light source being disposed over the outer surface ofsaid first light conducting element.

References Cited by the Examiner UNITED STATES PATENTS 2,561,881 7/1951Oetting 40-130 2,906,048 9/ 1959 Kraus 40-130 X 2,916,011 12/1959 Molis240-1 X 2,945,145 7/1960 Neugass 313-108 2,953,668 9/1960 Bassett 240-1X 3,083,317 3/1963 Fish et al. 40-130 X FOREIGN PATENTS 125,229 8/1947Australia.

816,795 5/ 1937 France. 1,047,713 7/ 1953 France. 1,186,348 2/ 1959France.

402,825 12/ 1933 Great Britain.

WALTER A. SCHELL, Primary Examiner.

IRVING BUNEVICH, Examiner.

CLYDE I. COUGHENOUR, Assistant Examiner.

1. AN INDICATOR ILLUMINATION SYSTEM COMPRISING AN INCANDESCANT LAMP AS AFIRST LIGHT SOURCE AND AT LEAST ONE ELECTROLUMINESCENT ELEMENT AS ASECOND LIGHT SOURCE, INDICIA TO BE ILLUMINATED, SAID ELECTROLUMINESCENTELEMENT COMPRISING AN OPAQUE LIGHT SHIELD ON ONE SURFACE THEREOF ANDINTERPOSED BETWEEN SAID LIGHT SOURCES AND SAID INDICIA TO PROHIBITDIRECT LIGHTING OF SAID INDICIA BY SAID LIGHT SOURCES, A REENTRANT LIGHTCONDUCTING CIRCUIT EXTENDING FROM SAID LIGHT SOURCES TO SAID INDICIAWHEREBY LIGHT ENTERING SAID CIRCUIT FROM SAID LIGHT SOURCE IS CONDUCTEDTHROUGH SAID CIRCUIT TO ILLUMINATE SAID INDICIA AND IS RECIRCULATEDTHROUGH SAID CIRCUIT TO ENHANCE THE ILLUMINATION, SAID REENTRANT LIGHTCONDUCTING CIRCUIT COMPRISING A FIRST LIGHT CONDUCTING ELEMENT INT WHICHLIGHT FROM SAID LIGHT SOURCES IS INJECTED, AND A SECOND LIGHT CONDUCTINGELEMENT FOR CARRYING ILLUMINATION TO SAID INIDICA AND COOPERATING WITHSAID FIRST LIGHT CONDUCTING ELEMENT TO RECEIVE LIGHT THEREFROM, AND OENOF SAID LIGHT CONDUCTING ELEMENTS HAVING LIGHT REFLECTIVE FACETS ADAPTEDTO CARRY LIGTH AROUND SAID OPAQUE LIGHT SHIELD.